1. Field of the Invention
The present invention relates to a color filter substrate, and a liquid crystal display panel comprising the color filter substrate stacked on a counter substrate through a seal material.
2. Background Art
A retardation film for controlling a phase difference has hitherto been used in liquid crystal displays. For example, in the reflection-type liquid crystal, display, in general, a linearly polarizing plate and a ¼λ retardation plate are used in combination to provide circularly polarized light. Further, in recent years, in a liquid crystal display of a homeotropic alignment mode widely used in liquid crystal TV applications, in order to reduce the dependency of display upon the angle of visibility, a retardation film having an optical axis perpendicular to the substrate and having a negative birefringence anisotropy (a negative C plate) and a retardation film having an optical axis horizontal to the substrate and having a positive birefringence anisotropy (a positive A plate) are used in combination. Many other retardation films are commercially available including view angle compensation films using discotic liquid crystals.
All the above conventional retardation films are applied to the outer side of the liquid crystal cell. In this case, for the reason that different retardation films, or a retardation film and a polarizing plate are applied to each other at a certain specific angle and for the reason that the refractive index of a pressure-sensitive adhesive for application is different from the refractive index of the retardation plate and the refractive index of the polarizing plate, external light reflection occurs at the lamination interface, leading to lowered display contrast.
In recent years, an attempt has been made to provide a retardation layer utilizing a liquid crystal material within a liquid crystal cell (Japanese Patent Laid-Open No. 48627/1998). Such liquid crystal materials usable herein include, for example, liquid crystalline polymers having a glass transition point and capable of freezing the liquid crystal structure at or below the glass transition temperature, and liquid crystalline monomers which can cause three-dimensional crosslinking in a liquid crystal layer state utilizing a reactive group such as an unsaturated bond in a molecular structure and consequently can freeze the liquid crystal structure. The liquid crystal materials can be applied by coating onto a base material having an aligning function. The retardation layer provided within the liquid crystal cell can eliminate the drawbacks of conventional retardation films of a type applied to the outside of the liquid crystal cell.
When a retardation layer is provided on the inner side of the liquid crystal cell, the retardation layer is provided on any one of a pair of substrates constituting the liquid crystal cell. Typically, the retardation layer is provided on the inner side of a color filter substrate with a color filter. The liquid crystal cell is constructed so that a color filter substrate and a counter substrate are provided in combination and a liquid crystal material is filled into between the substrates. Both the substrates race each other while providing a given space therebetween, and the peripheral part of the substrates are sealed with a seal material.
When a retardation film is provided on the outer side of the liquid crystal cell as in the prior art, both the substrates on their inner sides (liquid crystal material filling sides) are intimately contacted with each other through a seal material. When a retardation layer is provided on the inner side of the liquid crystal cell, however, for the retardation layer and the seal material, mutual positional relationship and mutual adhesion should be taken into consideration.
For example, in a color filter substrate, in fact, a black matrix layer is sometimes provided on the peripheral part of the display area for displaying an image. The reason why the black matrix layer is formed in a picture frame form is attributable to the production process, that is, is that, in the formation of a black matrix layer using a black pigment-containing resin composition or a thin film of a black metal such as chromium, the black layer is first provided on the whole area of the substrate followed by the removal of the black layer only in its part corresponding to the display part for patterning. This picture frame part functions to prevent light leakage. When a seal material is located in the black matrix layer iii its picture frame part, the adhesion between the substrate and the black matrix layer, the adhesion between the black matrix layer and the retardation layer, and the adhesion between the retardation layer and the seal material should be well ensured.
When a base material, a black matrix layer, a retardation layer, and a seal material participate in the part to be sealed, the adhesion between the substrate and the black matrix layer and the adhesion between the black matrix layer and the retardation layer are not always satisfactory. In particular, when the black matrix layer is formed of a black pigment-containing resin composition, in some cases, the adhesion between the substrate and the black matrix layer and the adhesion between the black matrix layer and the retardation layer are not sometimes satisfactory, often resulting in separation in the seal part.